Hey guys, I'm having quite some problems with memory on my PC. I'm guessing it could be some sort of memory leak. Ok so here's what happening:

Since a few week my memory usage is never really decreasing, I boot my PC just fine with 1GBish of RAM usage, than I will run some games or programs and my memory usage will go up (obviously), but the problem is that it doesn't really decrease when I'm done with them. Say I go play some stalker Clear Sky, when I'm done I exit and look at my memory consumption on Idle and it'll be around 2.5GB of RAM BEING used, an that's on Idle. (it's not related to stalker itself, it does that with pretty much everything that uses memory).
I'm using Vista x64 on SP2

I decided to post because I was just installing Oblivion a few minutes ago and when it has been done installing I had 150ish MB of memory left, out of 4GB. I waited for a few minutes, and it stayed this way. I looked in the task manager and nothing was wrong in it. I rebooted and started writing this thing.

So ya if you guys can't find the problem of w/e is causing this, I guess I'll just format my PC, it's been a long time since I did it anyway so it has to be done. But still I want to know what's wrong.

That's how Vista is designed. To gobble up as much memory as you provide it with. It keeps things in memory in case you want to use them again in the near future. If you start another application that needs memory, then it will free up the stuff that's not being used. Start up Prime95 and see how much memory it finds to use when you use the Blend option.